vaillant boiler is displaying fault S33? ?

This is an excellent forum !

Terranss
January 2016

So I'm sitting around depressed because the house is cold - I have this S33 problem - and my team just lost . After reading all the advice here I concluded I have an Air Pressure Switch fault .
On ebay there's a used one for £7 but I go and try to find my APS just to check .
I take the white metal cover off the boiler . I unclip the 3 clips holding the aluminium sheet with " Vaillant " stamped onto it and I gently pull that sheet of aluminium off . And the boiler fires up straight away !!!!!!
Don't ask me to explain . Maybe what I did was wrong . But my house is warming up very nicely .

Thank you men !!!!!

Terranss
January 2016

Aps , fan Venturi , flue & even pcb can give the fault.. Most common issue is the APS & fan Venturi ,,, have on one occasion had this fault due to faulty pcb ......
Always get a registered engineer to fix....

Andy Bhoy
December 2012

As stated below, Have an acredited boiler service engineer that knows the model to fix the boiler, they may ask you the make and model Number of the boiler. It may be adviseable to ask for the boiler to be serviced and fix the problem at the same time to save an additional call out fee and more importantly peace of mind that it should work for a while afterwards without fail. I have the local gas company service the boiler as they charge the same as local "experts" who have charged me £50 to "blow into an air pressure pipe" taking 5 minutes tops previously! A gas company engineer may check the gas and meter but all engineers should measure exactly the power output the boiler is giving for both hot water and for the central heating..
Here is a link to a TurboMax manual, it may not be correct for your model but could be generally informative..(general concensus- call in an expert) Good Luck ;-) http://www.ultimatehandyman.org/PDF/vaillant/Thermo-compact.pdf

Dave again
July 2011

Download a vaillant manual relating to your boiler model if possible.. they have all the ruuning error codes and diagnostic codes which are easy for the novice to check in real time(whilst the boiler is running) without risk of problems.. the unit as stated S33 can be casued by a few things not working prior to ignition sequence. The air pressure switch detects air pressure accross the fan - eg that the fan is working and moving sufficient air to permit boiler operation.. Typically when the fan is running two tubes connect the fan air across the fan to the simple air pressure swich (needs sufficient pressure to operate- there is a diagnostic setting that will show if switch is "on or "off").. I found on a 6 year old boiler that this air pressure switch has decided to be unreliable.. whether it is the fan caking up a bit or the switch, I checked it was the swich by - turn off gas, turn off mains power/ wait five mins, get to top of boiler/ pull air pressure switch off from its plastic lug carefully- it has two wires on it, disconnect one of the tubes, carefully blow into pressure switch nozzle until it clicks (or suck gently if the other pipe-one is blue and one white) reconnect pipe/ refit air pressure switch/ re clip to boiler/ mains on/ gas on -run hot water to reboot boiler.. confirmed was switch as now passes the fan check stage - calling out gas engineer to replace switch and service the boiler.. seriously get the "Instructions for Installation and servicing".. really helps to understand..

Dave
July 2011

boilers follow a sequence, one part fails the boiler does not work. could be pcb, could be fan, air pressure switch all of which happen before boiler will attempt to ignite, get in an expert is what I would recommend

rawplumb
March 2010